Production of alkali-metal cyanides



Dec., 26, 1922.

F. J.' METZGER. PRODUCTION 0F ALKALI METAL CYANIDES.

man M'An.23. 1920.

Residue Patented Der. 26, i022.;

uit sans ari FLOYD J. innrzenn., or New Yoan, N. Y.,

rinata nr eric.

ASSIGNOR T0 AIR REDUCTION COMPANY,

NC., A CORPORATION OF NEW YORK.

PRODUCTION OlE ALKALI-METAL CYANIDES.

.application filed March 23, 1920.

exact description ofthe invention, such` as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to the production of high .grade alkali metalcyanides by the fixation of nitrogen and particularly to the recovery of cyanides from furnace products resulting from the heating of mixtures of alkali metal carbonates. or oxides and carbon, with or without a catalytic agent such as iron, in the presence of nitrogen or nitrogenous gases.

Methods of the character described, for example, in United States Letters Patent No. 1,322,195, have been developed to produce a furnace product containing upward to thirty per cent of alkali metal cyanide, the balance consisting of alkali metal carbonate and oxide, carbon and iron, and in U. S. Letters Patent No. 1,385,336,21. method of converting the cyanide intro hydrocyanic acid is described. The hydrocyanic acid thus released may be liquefied and utilized as such, but the numerous uses of alkali metal cyanides in pure or substantially pure condition suggests the desirability of recombining the acid with an alkali metal.

Thev object of the present invention is, therefore, to provide a method whereby alkali metal cyanides may be produced in a simple and satisfactory manner from crude furnace products such as are described in the patent above referred to and to permit the utilization of all of the products of the several reactions so that the method is economical and therefore, comn'lercially practicable.

The invention has its foundation in the discovery thatthe reaction which is depended upon to free thel hydrocyanic acid from the furnace product may be reversed under suitable temperature conditions which are readily controlled. Thus,.in the converter, the furnace product is treated with carbon dioxide preferably traversing the mass at a rate which precludes the formation of polymers of the acid. The same result Serial No. 368,101.

maybe accomplished, however, by suitably controlling the temperature of the mass during the contact of carbon dioxide therewith as described in U. S. Letters Patent No. 1,385,385. The hydrocyanic acid is released as such and the residue may be returned to form the basis of mixtures for the cyanide furnace. The hydrocyanic acid may 'then be caused to react with an `alkali metal compound, preferably the carbonate, while the mass is held at a temperature varying from 200o to 500O C. with the result that the alkali metal cyanide is produced in a condition of purity depending on the purity of the alkali metal compound used while carbon dioxide is released, and may be returned for use in the converter to release further quantities of hydrocyanic acid.

In the accompanying drawing, l have provided a iiow sheet which illustrates the preferred mode of practicing the invention. Referring to the. drawing, an alkali metal compound such as the carbonate or oxide is mixed with carbon and a proportion of iron, preferably in the form of an oxide. The proportions may vary but a typical example requires 44 parts of alkali metal carbonate or oxide, 54 parts of carbon such as coke, and two parts of iron in the form of an oxide. The materials are thoroughly commingled in a suitable mixer, being preferably moistened sufficiently to cause the particles to agglomerate. The` mass is then dried and is delivered to the furnace where it is subjected to a relatively high temperature, e. 950-1100o C., while nitrogen or nitrogenous gases are passed through the furnace in contact with the mass. thel reaction has proceeded to the point which is determined by 4a 'study of the conditions of maximum production in a minimum time, the furnace product is discharged to a con- .verter where the mass is 'moistenedand subjected to the action of carbon dioxide. The carbon dioxide is preferably forced through the mass at a comparatively high rate precluding the formation of polymers of hydrocyanic acid. The reaction is indicated as follows:

zivacN H,o cof-anon Nace,

land oxide, carbon and iron is returned to furnish lthe basis of new mixtures until `it When y becomes contaminated with ash from th carbon. The hydrocyanic acid mixed with the excess of carbon diox-ide used, may be condensed and utilized as such but the purpose of the present invention is to produce cyanides and accordingly the mixed gas is delivered to a chamber in Which the hydrocyanic acid reacts with an alkali metal compound, preferably a carbonate. The temperature of the chamber is maintained between 200O and 500o C. and at a point which permits the reversal of the reaction previously employed to free the acid. The result is an alkali metal cyanide, and carbon dioxide which is returned for use in the converter to release more hydrocyanide acid.

From the foregoing it will be apparent that the method described has the advantages of simplicity and economy. All of the materials are handled in a dry condition and there are no by-products except the waste gases from the cyanide furnace and that portion of the residue which eventually becomes contaminated with ash. Aside from replacements of alkali metal compound and iron thus required, the only materials re quired are carbon, nitrogen and the alkali metal compound which forms the linal basis of the cyanide. Carbon dioxide is generated in substantially sufficient quantity to supply the converter and any additional supply rei-ired may be drawn from a suitable source. product of considerable value is made from relatively cheap materials, the princivpal cost factors being the heat-and labor retails of the method and the proportioning` of the material employed Without departing from the invention or sacrificing any of its advantages.

I claim:

l. A method of recovering' alkali metal cyanide from crude furnace products, which comprises subjecting the solid furnace product to the action of carbon dioxide under conditions precluding the polymerization of the hydrocyanic acid released. and subsequently combining* the hydrocyanic acid with a solid alkali metal compound while the compound is maintained at a temperature between 200O and 500O C.

2. A method of recovering.r alkali metal cyanide fromy crude furnace products. which comprises subjectingA the solid furnace product to the action of carbon dioxide under conditions precludinp` the polymerization ot the hydrocyanic acid released. subsequently combining' the hydrocyanic acid with asolid alkali metal carbonate while the carbonate is maintained at a temperature between 200o and 5000 C.. and returning' the carbon di oxide released to decompose further quantities of the furnace product.'

ln testimony whereof I affix my sig-nature,

FLGYD J. METZGER. 

